1. Field of the Invention
The present invention relates generally to light deflection mechanisms and more specifically to galvanometers of the type used in an oscillograph for providing a permanent record of a plurality of energizing signals introduced to the galvanometers.
2. Description of the Prior Art
An oscillograph is an instrument having a light source providing a beam of light and a photosensitive paper movable in the path of the beam of light and having photosensitive properties responsive to the beam of light to provide a trace on the paper. A galvanometer assembly, positioned between the light source and the photosensitive paper in the path of the beam of light, includes a mirror which deflects the beam of light in a direction transverse to the movement of the paper. The deflection of the mirror is in accordance with the characteristics of an energizing signal introduced to the galvanometer. Thus the greater the magnitude of the signal, the greater the deflection of the light beam. As the light beam is deflected, it provides the trace on the photosensitive paper with characteristics representative of the characteristics of the energizing signal.
The galvanometer assembly typically includes a coil which is suspended with the mirror between a pair of wires. The coil is positioned within an air gap defined by pole pieces attached to a large permanent magnet. The coil is energized through the suspending wires by the energizing signal to be recorded. This signal produces an electromagnetic effect in the coil which aids or opposes the magnetic field produced by the permanent magnet to deflect the coil and the attached mirror. A galvanometer assembly of this type is disclosed and claimed by Richardson in his U.S. Pat. No. 3,599,611, assigned of record to the assignee of record of the present application.
In the past, each of the galvanometers have been separately constructed and encased. Each galvanometer has been provided with its own secondary pole pieces which have registered with grooves in a pair of primary pole pieces associated with the permanent magnet. As a result of this individual construction, the cost per channel of the galvanometer assembly has been relatively high. In addition, each of the galvanometers has been separately mounted so that any alignment of the galvanometers with respect to each other has been carried out by the user rather than the manufacturer. In some cases, the coils associated with the galvanometers have been mounted in tubes filled with oil. In this configuration, the oil has tended to damp any undesirable oscillations of the coil and mirror. A heater assembly has been used to maintain the temperature of the oil so that its viscosity tends to remain substantially constant.
Although these oscillographs and galvanometer assemblies have provided excellent means for recording signals, it is always desirable to minimize the cost per channel. In addition, it may be desirable to provide means for simultaneously aligning all of the galvanometers in a single oscillograph.